1. Field of the Invention
The present invention relates to a coupling system utilized in connecting end-to-end lined pipe used in oil wells and the like, and, more particularly, a liner assembly for use in a joint between two pipe segments and a method of connecting two unmodified pipe segments with a linear system which will prevent corrosion.
2. Description of Related Art
Many downhole oil-production operations are carried out in highly corrosive environments resulting from production and/or re-injection of hydrocarbons and formation of brinewaters containing salts and gases, such as hydrogen sulfide and carbon dioxide which can pass through the pipe interior.
To provide a useful life to the lengths of steel pipes that are used in such environments, corrosive resistant liners are installed within each pipe length before it is installed into the downhole string. Appropriate threaded coupling assemblies are required to connect the pipe in an end-to-end relationship. Coupling assemblies are also required to connect the internal liners that provide protection for the pipe and pipe threaded connection area against internal corrosion.
There are a large number of pipe end constructions and thread constructions employed by various pipe manufacturers to assure against fluid and gas leakage. Due to the presence of unique metal-to-metal torque shoulders and metal-to-metal seal areas, many of these pipe end and thread constructions known in the art require a custom built liner or coupling assembly unique to the pipe end and potentially even a custom pipe end thread design to accommodate an internal lining system.
One method known in the art utilizes an internal lining system that requires the insertion of a rigid plastic tube inside steel tubing and filling the annular space between the plastic tube and steel tubing with mortar. The inner rigid plastic tube, or liner, is capped or terminated at the end of the pipe with a flange, known as a “flare”. The flare ends provide a surface area for compression of a barrier ring, such as an elastomeric barrier ring, in the coupling assembly.
An obstacle with insertion of such an assembly is that the threaded pipes or couplings need to be machined and threaded with special provisions to accommodate the lining process. This proves to be ineffective in time and cost as well as productivity.
Additionally, it has been discovered that when such liner systems are used in high temperature and pressure environments, the movement of the fluid through the pipes causes the liner to move or shift slightly within the pipes. This movement of the liner causes exposure of the grout or mortar positioned behind the liner. Such exposure erodes the grout or mortar and eventually corrodes the pipe.
In view of the foregoing, there is a need for a standardized or universal internal liner coupling assembly that can accommodate the wide variety of pipe end constructions currently in use without the need for special modifications to proprietary pipe end threads and couplings. There is also a need for a liner coupling assembly that can accommodate the liner, particularly at high pressures, thereby preventing grout or mortar exposure while at the same time preventing liner movement.